Question

Major League Baseball now records information about every pitch thrown in every game of every season. Statistician Jim Albert compiled data about every pitch thrown by 20 starting pitchers during the 2009 MLB season. The data set included the type of pitch thrown (curveball, changeup, slider, etc.) as well as the speed of the ball as it left the pitcher’s hand. A histogram of speeds for all 30,740 four-seam fastballs thrown by these pitchers during the 2009 season is shown below, from which we can see that the speeds of these fastballs follow a Normal model with mean μ = 92.12 mph and a standard deviation of σ = 2.43 mph.

A)Compute the z-score of pitch with speed 89.9 mph. (Round your answer to two decimal places.)

B)Approximately what fraction of these four-seam fastballs would you expect to have speeds between 86.5 mph and 93.7 mph? (Express your answer as a decimal, not a percent, and round to three decimal places.)

C)Approximately what fraction of these four-seam fastballs would you expect to have speeds above 93.7 mph? (Express your answer as a decimal, not a percent, and round to three decimal places.)

D)A baseball fan wishes to identify the four-seam fastballs among the slowest 2% of all such pitches. Below what speed must a four-seam fastball be in order to be included in the slowest 2%? (Round your answer to the nearest 0.1 mph.)

Answer 1

solution : - Given mean us 92.12 Standard deviativo 02:43 a) z score for 198919 2 4. 89.9 -92612 -0.91 2:43 2=-0,91 (Rounded to adeunal place) b) 243 PC86.5 crc93.7): - 8615- 92012 93.7 - 92.12 - PC 8GB dru3 :((-2. 31 2 8 4 2 0 6 3 0 9) --P (-2.31 CZC0.65) = P(Zc0165) - PC Zc-2:31 Or47425 - Odovy => 017317 Ñ 01732 C Rounded to. 3deamal place) (Frell x 93.7-9212 2:03 P (x=93-7) - PC270.65 El-P(Z < 0.615) => 1 - 01768215 - 0125785 à 01258 CRounded to three decimal placed) d) P(x<K) = 0.02 P(Ec K-92112 20.02 2.43 K-92112 2.03 -2.05 xok (62-108) 2043] 492012 Ke 87.1985 K:84: 1 mph